Cancer-related Fatigue

What is Cancer-related Fatigue?

There is an extremely high incidence of fatigue in people with cancer. It is the number one symptom reported by patients undergoing chemotherapy affecting up to 80%. The next most common symptom in patients undergoing chemotherapy is nausea with an incidence approaching 55% [1].

Cancer-related fatigue can severely impact a cancer patient’s quality of life by depressing their mood, decreasing alertness, and significantly limiting physical activity [2]. For many people living with cancer, cancer-related fatigue may be their most distressing symptom. Unfortunately, it is usually not properly addressed by the caregiving team.

Brain fog, which also goes by the name “chemo brain”, is another distressing symptom that may frequently occur after cancer patients receive chemotherapy. A study published in the Journal of Clinical Oncology found that the cognitive recovery after chemotherapy for breast cancer can take up to five years or more [3].

Karen L. Syrjala, the study’s lead author says that “people need to understand the extent to which the cells in their bodies have really been compromised by not only the cancer, but also the treatment.”

How is Cancer-related Fatigue Linked to Mitochondrial Dysfunction?

Cancer chemotherapy drugs make up the most powerful cellular toxins used in medicine. Their goal is to kill fast growing cancer cells while imparting somewhat less toxicity to healthy cells. Unfortunately, healthy cells of the body are also affected by chemotherapy toxicity to a degree. This leads to many common chemotherapy side effects such as fatigue, brain fog, peripheral neuropathy, and anemia.

Paclitaxel (Taxol®) is a cancer drug derived from tree bark commonly used for to treat solid tumors such as breast, ovarian and lung cancers. After paclitaxel treatment, the electron gradient across the mitochondrial inner membrane is altered leading to swollen and vacuolated mitochondrial appearance. This damage to the mitochondria supports the mitotoxicity hypothesis, which suggests that paclitaxel produces a chronic sensory neuronal energy deficiency that may be the primary cause of peripheral neuropathy side effects linked to this drug [4,5].

The following chemotherapy drugs have now been implicated in contributing to mitochondrial toxicity [6]:

Paclitaxel

Cisplatin

Oxaliplatin

Vincristine

Bortezomib

In addition to directly damaging nerves and causing peripheral neuropathy, the toxic effects of chemotherapy on the mitochondria may also be contributing to the fatigue and decreased cognitive function experienced by patients after receiving chemotherapy.